Generation and Reaction of Alkene Radical Cations under Nonoxidizing Conditions: Synthesis of the Pyrrolizidine Nucleus.

Stable β-phosphatoxy nitroalkanes, readily assembled by the Henry reaction and subsequent phosphorylation, serve as good precursors to alkene radical cations on treatment with triphenyltin or tributyl hydride and AIBN in benzene at reflux. When the β-phosphatoxy nitroalkane is suitably functionalized with nucleophilic groups, substitutions can be achieved with the formation of heterocyclic rings. When the nucleophile is an allylamine, tandem processes occur giving pyrrolizidines.